Foreign matters on a semiconductor substrate (wafer), if any, may result in defects of wiring such as inferior insulation and short-circuit in a semiconductor manufacturing process. When a semiconductor device is miniaturized and fine foreign matters exist inside the semiconductor substrate, the foreign matters may result in an insulation defect of a capacitor and breakdown of a gate oxide film. These foreign matters are generated owing to diversified causes such as those which occur from movable portions of a conveyor apparatus and from the human body, those which are generated due to the reaction inside a processing apparatus using process gases and those which are mixed in chemicals and materials, and are mixed under diversified conditions. A defect inspection device is known as a device for inspecting these foreign matters and includes an illumination optical system, a detection optical system and an image processing system.
The paper “Broadband alignment scheme for a stepper system using combinations of diffractive and refractive lenses”, Applied Optics, v. 33, No. 34, pp 7971-7979(1994) describes the use of a plurality of wavelengths for reducing the change of light power resulting from the change of a film thickness in the illumination optical system. To correct chromatic aberration necessary for acquiring high resolution images using a plurality of wavelengths, U.S. Pat. No. 6,560,039 B1 teaches that Schwarzschild catoptrics objective lenses (catoptrics objective lenses) are more effective than dioptrics objective lenses.
“Polarization Control for Enhanced Defect Detection on Advanced Memory Devices”, Proceeding of SPIE Vol. #6152(2006) describes a method for accomplishing defect detection with high sensitivity by radiating illumination light to a wiring short-circuit unit at the bottom of a semiconductor substrate by illumination. Because a Schwarzschild catoptric objective lens has a reflecting film or a reflecting surface at a lens center, however, vertical illumination cannot be made by using the Schwarzschild objective lens. Therefore, U.S. Pat. No. 6,954,266 B2 discloses a method for vertically radiating rays of light from a light source onto a sample by arranging a mirror between a Schwarzschild objective lens and a sample surface or a mirror between a Schwarzschild objective lens group and a detector.
JP-A-10-177139 describes an illumination and detection method for detecting foreign matters adhering to a sample through a catadioptric objective lens by radiating light from a light source onto the sample by inclined illumination or vertical illumination.